The invention relates to a load-adjustment device having a control element (11) which can act on a throttle valve (e.g. 16) of an internal combustion engine, and which is connected to a driver (4) which is coupled to an accelerator pedal (1) and, in addition, can be moved by means of an electric setting drive (9), having a desired-value detection element (7) associated with the driver and an actual-value detection element (12) which cooperates with the desired-value detection element (7) and acts on the electric setting drive, the electric setting drive being controllable as a function of the detected values of an electronic control device (22).
Load-adjustment devices of this kind are provided for the actuation of the throttle valve by the accelerator pedal so as to be able so to intervene by means of the electronic control device that, for instance, wheel slippage resulting from excessive power upon starting is avoided. The control device provides that upon excessively rapid depression of the accelerator pedal, the throttle valve, for instance, is opened less than corresponds to the position of the accelerator pedal, so that the internal combustion engine produces only an amount of power which does not lead to spinning of the wheels. Other automatic interventions into the load-adjustment device are necessary if a transmission is to be shifted automatically or the engine idling speed of rotation is to be set to a value which is constant even when different powers are required upon idling. It is also known in the case of such an adjustment device to intervene by a speed-limiting controller which can provide, by the possibility of uncoupling the control element from the accelerator pedal, that in each case that power is set which is necessary in order to maintain the speed set. In addition, it may be desirable, particularly from the standpoint of comfort in driving, to provide a progressive or degressive connection of the accelerator pedal, with the possibility of reduced or increased power setting as compared with the position of the accelerator pedal.
Safety factors, however, make it necessary to provide assurance, even in the event of a defect in the control device, that upon retraction of the position of the accelerator pedal, the power setting decreases synchronously with the position of the accelerator pedal. This is achieved by safety devices in the electronic control device. Possibilities of error in the control device are reduced in the manner that the electronic system is developed redundantly. Nevertheless, too high a power setting which does not correspond to the position of the accelerator pedal is not completely excluded in the event that a defect is present.
Load-adjustment devices of the foregoing type are generally developed with several parts, i.e. given elements are associated with the accelerator perdal while other elements cooperate with the control element. Such a separate arrangement of the parts means, on the one hand, an increased structural size of the load-adjustment device while, on the other hand, due to the arrangement of the parts at different places of the vehicle, there is no assurance that the parts cooperate with the throttle valve without reaction.